The invention relates to a fluid power linear drive whose housing contains a piston able to be displaced by fluid actuation and furthermore an electrically activated control valve means for the control of the fluid actuation.
A linear drive disclosed in the European patent publication 0 713 980 A2 of this type comprises a central piston receiving space extending in the longitudinal direction and in which a piston is arranged which is connected with a piston rod. For the operation of the piston pressure medium may be admitted in a controlled fashion, for which purpose a control valve means is present, which includes several control valves inserted like cartridges into the covering lid of the housing of the linear drive. The activation of the control valves takes place by the intermediary of electronic valve control circuitry, which is also secured in the housing.
This known linear drive does admittedly possess a high degree of integration of the functionally relevant components, but however is less suitable as a basis for the design of miniaturized structures. Accordingly one object of the present invention is to provide a linear drive, on the basis of which more compact sizes are possible while maintaining an integrated design.
This object is to be attained by a fluid power linear drive comprising a slab-like housing with an elongated cross sectional outline, in which slab housing a plurality of receiving spaces are located placed in a common housing plane adjacent to each other in the direction of the cross section""s longitudinal axis, a piston receiving space being provided at a first one of the two narrow sides of the housing, such piston receiving space extending in the longitudinal direction and containing a piston connected with an outwardly extending force output part while at the opposite second narrow housing side an electronic circuitry receiving space is provided, which contains electronic valve control circuitry, and between the piston receiving space and the electronic circuitry receiving space at least one valve receiving space for electrically operated control valve means is located, such control valve means serving for the control of the fluid actuation of the piston.
The linear drive accordingly possesses a housing, which may be designed to be extremely flat and is therefore termed a slab housing, wherein receiving spaces for the functionally relevant components are arranged longitudinally adjacent to each other in such a manner that they lie in a common plane coinciding with the cross sectional longitudinal axis of the slab housing, and the available volume of the slab housing is optimally employed. The piston receiving space is associated with one of the narrow sides of the housing with the result that on three sides there is a relatively small wall thickness, which if necessary renders possible reliable sensor detection of the piston position. The opposite narrow side of the housing is associated with a receiving space for electronic circuitry, such space containing the electronic valve control circuitry, which can generate the switching signals necessary for the actuation of the control valve means. The control valve means is seated, as considered in the direction of the longitudinal axis of the cross section of the slab housing, between the piston receiving space and the electronic circuitry receiving space so that on the one hand there are shorter signal paths to the electronic valve control circuitry and on the other hand there are shorter fluid paths to the piston receiving space. The linear drive together with its various components may be extremely simply installed, the overall structure being sturdy in conjunction with an extremely compact form, such overall structure being suitable for miniaturized applications.
Further advantageous developments of the invention are defined in the dependent claims.
The electronic valve control circuitry is preferably provided on a pcb-like (i. e. like a printed circuit board) electronic circuitry support, which is more particularly so inserted in the electronic circuitry receiving space that its board plane is at a right angle to the longitudinal axis of the cross section of the slab housing with the result that compact dimensions are adhered to in the longitudinal direction of the cross section.
In order to be able to link the electronic valve control circuitry with the control valve means in an optimum manner electrically, it is preferred to provide a uniform control receiving space divided up into sections, which on the one hand represent the valve receiving space and on the other hand the electronic circuitry receiving space.
On the longitudinal side, which is opposite to the valve receiving space, of the piston receiving space a sensor means receiving space may be provided, which contains a position detecting means for the detection of the piston position. This means preferably comprises one or more sensors able to be set in a variable manner in the longitudinal direction of the sensor means receiving space, such sensors being electrically connected with the electronic valve control circuitry. It is more especially advantageous for the position detecting means to possess a printed circuit board extending in the longitudinal direction of the sensor means receiving space, such board serving for the transmission of position signals from and/or to the sensors, which may be arranged on the printed circuit board in a manner allowing longitudinal adjustment.
Instead of a control valve means having a 5/2 switching function, which would also be possible, a design is to be particularly recommended with two separate control valve units, which respectively possess a 3/2 switching function and which are respectively responsible for the supply of fluid to the piston for driving same in one of the two possible directions of motion thereof. These two control valve units are preferably accommodated in the longitudinal direction of the slab housing one after the other in a common valve receiving space, it being possible to have a provision such that at least the valve drive signals for one control valve unit are also transmitted by way of the position detecting means so that same may assume a double function as regards transmission of electrical signals.
The slab housing of the linear drive preferably comprises a principal housing body, wherein the different receiving spaces are formed extending from axial one end to the other, a design in the form of an extrusion being more especially possible. The termination of the principal housing body may be in the form of lid-like coverings, which may simultaneously also perform the holding function as regards the component valve means. Between a respective covering and the principal housing body it is possible to fit a printed circuit board, which may be employed for signal transmission between the position detecting means and the electronic valve control circuitry and/or the control valve units.
The printed circuit board may be provided with sealing means, which serve to ensure a fluid-tight connection between the covering and the principal housing body and which in case of need may at least partially perform the function of light guide means in order to render the light signals visible from the outside. The light signal may for example indicate the state of activation of the control valve means and/or the piston position.
The linear drive is more particularly suitable for being fitted with a control valve means, whose valves are at least partly constituted by microvalves produced by micromaching, the use of piezoelectric valves also being possible.
It is furthermore an advantage if both the fluid and also the electrical terminals or connections of the linear drive are collected together on a common terminal side of the slab housing, such side preferably being the rear side which is opposite to the front side with the piston rod extending through it.